- Also called:
- Triassic-Jurassic extinction
end-Triassic extinction
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What was the end-Triassic extinction?
The end-Triassic extinction was a global event at the close of the Triassic Period, roughly 252 million to 201 million years ago, eliminating about 76% of marine and terrestrial species and 20% of taxonomic families. It ranks as the fourth most severe of the five major extinction episodes in geologic time.
The extinction particularly affected ammonoids and conodonts, as well as many families of brachiopods, gastropods, bivalves, and marine reptiles. On land, much of the vertebrate fauna disappeared, while dinosaurs, pterosaurs, crocodiles, turtles, mammals, and fishes were little affected. Many maintain that this mass extinction on land opened ecological niches quickly filled by dinosaurs.
The cause of this event is debated, but many scientists believe that climate change and rising sea levels from the release of large amounts of carbon dioxide may have been the cause.
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When did the end-Triassic extinction take place?
The end-Triassic extinction took place approximately 252 million to 201 million years ago, at the close of the Triassic Period. This global event led to the demise of about 76% of marine and terrestrial species and roughly 20% of taxonomic families and ranks as the fourth most severe of the five major extinction episodes in geologic time.
Many scientists believe that the cause of the end-Triassic extinction was climate change and rising sea levels due to the release of large amounts of carbon dioxide from the rifting of the supercontinent Pangea.
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What kinds of organisms were affected by the end-Triassic extinction?
The end-Triassic extinction event, which occurred approximately 201 million years ago, led to the demise of about 76% of marine and terrestrial species.
The extinction particularly affected ammonoids and conodonts, with many Triassic ceratitid ammonoids and the conodonts going extinct. Only the phylloceratid ammonoids survived, later leading to a cephalopod radiation in the Jurassic Period. Additionally, numerous families of brachiopods, gastropods, bivalves, and marine reptiles also disappeared.
On land, a significant portion of the vertebrate fauna vanished. However, groups like dinosaurs, pterosaurs, crocodiles, turtles, mammals, and fishes experienced little impact. Plant fossils and palynomorphs showed no significant diversity changes across the Triassic-Jurassic boundary.
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What do scientists think caused the end-Triassic extinction?
Scientists believe that the end-Triassic extinction was caused by climate change and rising sea levels, which resulted from the release of large amounts of carbon dioxide due to the rifting of the supercontinent Pangea. Studies estimate that this rifting may have released up to 100,000 gigatons of carbon dioxide, strengthening the global greenhouse effect, increasing average air temperatures, and acidifying the oceans.
Some scientists suggest that the heating caused by rising carbon dioxide concentrations could have released massive amounts of methane, a more effective greenhouse gas, from permafrost and undersea ice, which could have significantly warmed Earth’s atmosphere. Others propose that the extinction was triggered by an extraterrestrial impact. Some argue that the end-Triassic extinction was simply a prolonged turnover of species and not a mass extinction event.
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How did the end-Triassic extinction change life on Earth?
The end-Triassic extinction, one of Earth's major extinction events, occurred about 201 million years ago and eliminated approximately 76% of marine and terrestrial species. While less devastating than the Permian extinction, it drastically reduced populations, particularly affecting ammonoids and conodonts, though phylloceratid ammonoids survived. On land, much of the vertebrate fauna disappeared, but dinosaurs, pterosaurs, crocodiles, turtles, mammals, and fishes were largely unaffected, allowing dinosaurs to quickly fill vacant ecological niches. Plant diversity remained largely unchanged. This extinction paved the way for the Jurassic Period, marked by the dominance of dinosaurs and the emergence of modern biological groups.
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Why is the end-Triassic extinction important for understanding Earth’s history?
The end-Triassic extinction, occurring roughly 201 million years ago, is significant because it paved the way for dinosaurs to become the dominant land animals. This event, ranking fourth in severity among major extinction episodes, drastically reduced marine and terrestrial species, affecting ammonoids and other groups.
The end-Triassic extinction is thought to have been caused by climate change and rising sea levels due to the release of large amounts of carbon dioxide from the rifting of the supercontinent Pangea. Resulting volcanism may have increased average air temperatures and acidified the oceans. This extinction event is a key moment in understanding the evolution and distribution of life on Earth.
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end-Triassic extinction, global extinction event occurring at the end of the Triassic Period (about 252 million to 201 million years ago) that resulted in the demise of some 76 percent of all marine and terrestrial species and about 20 percent of all taxonomic families. It is thought that the end-Triassic extinction was the key moment that allowed dinosaurs to become the dominant land animals on Earth. The event ranks fourth in severity of the five major extinction episodes that span geologic time.
(Read E.O. Wilson’s Britannica essay on mass extinction.)
Although this event was less devastating than its counterpart at the end of the Permian Period, which occurred roughly 50 million years earlier and eliminated more than 95 percent of marine species and more than 70 percent of terrestrial ones (see Permian extinction), it did result in drastic reductions of some living populations. The end-Triassic extinction particularly affected the ammonoids and conodonts, two groups that serve as important index fossils for assigning relative ages to various strata in the Triassic System of rocks. Indeed, the conodonts and many Triassic ceratitid ammonoids became extinct. Only the phylloceratid ammonoids were able to survive, and they gave rise to the explosive radiation of cephalopods later in the Jurassic Period. In addition, many families of brachiopods, gastropods, bivalves, and marine reptiles also became extinct. On land a great part of the vertebrate fauna disappeared, although the dinosaurs, pterosaurs, crocodiles, turtles, mammals, and fishes were little affected by the transition. In fact, many authorities maintain that the end-Triassic mass extinction on land opened ecological niches that were filled relatively quickly by dinosaurs. Plant fossils and palynomorphs (spores and pollen of plants) show no significant changes in diversity across the Triassic-Jurassic boundary.
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The cause of the end-Triassic extinction is a matter of considerable debate. Many scientists contend that this event was caused by climate change and rising sea levels resulting from the sudden release of large amounts of carbon dioxide. Studies estimate that the rifting of the supercontinent Pangea, where eastern North America met northwestern Africa, may have released up to 100,000 gigatons of carbon dioxide, which likely strengthened the global greenhouse effect, increasing average air temperatures around the globe by as much as 10–15 °C (18–27 °F) and acidifying the oceans. Modern studies examining the region’s flood basalts generated by this rifting reveal that the rocks were created during a 620,000-year interval of volcanic activity that occurred at the end of the Triassic. The volcanism of the first 40,000 years of this interval was particularly intense and coincided with the beginning of the mass extinction some 201.5 million years ago.
Other authorities suggest that the relatively modest heating caused by rising carbon dioxide concentrations in the atmosphere could have liberated massive amounts of methane trapped in permafrost and undersea ice. Methane, a much more effective greenhouse gas than carbon dioxide, could have then caused Earth’s atmosphere to warm significantly. In contrast, others maintain that the mass extinction was triggered by the impact of an extraterrestrial body (such as an asteroid or comet). There are also some who argue that the end-Triassic extinction was not the product of a single major event but simply a prolonged turnover of species across a considerable amount of time and thus should not be regarded as a mass extinction event.